The present invention relates to a hydroforming device which processes a raw material by hydraulic pressure. Preferably, the present invention relates to a hydroforming device which processes a steel pipe into a automobile component. Additionally, the present invention relates to a hydroforming method which uses the hydroforming device of the present invention.
A conventional method for achieving high pressure using a hydraulic intensifier is disclosed in xe2x80x9cPipe Working Methodxe2x80x9d, by Masanobu Nakamura, published by Nikkan Kogyo Shinbun Co. (Jan. 31, 1996). A further example of a conventional hydroforming device is disclosed in Japanese Laid-Open Patent Number 9-314240 (Japanese Patent Application Number 8-194175).
According to these conventional devices, when molding a steel pipe, the closing of the upper and the lower mold is conducted by a single closing cylinder disposed on the crown on the press machine. With this construction, in order to have the required closing force, the closing cylinder must have a large diameter and a large stroke length. As a result, the closing cylinder becomes a cylinder with a large volume. This type of construction is disadvantageous from the standpoint of high speed and responsiveness. In other words, the time needed for the closing motion is relatively long, thereby increasing production time.
Other conventional hydroforming devices process steel pipes by sending a high pressure fluid inside the pipe. In these hydroforming devices, by stroking a closing cylinder, an upper mold is raised and lowered, to supply the material inside the mold as well as to perform maintenance of the mold. As a result, it is necessary to manufacturer a press machine that is used exclusively for hydroforming.
For example, in Japanese Laid-Open Patent Publication Number 5-329693, a hydroforming press machine is disclosed that has a bed attached to a floor surface. Four columns pass through the bed in a freely vertically sliding manner. A crown is provided at the upper end of the columns. A lower frame is provided at the lower end of the columns. Four hydraulic cylinders drive the lower frame in a vertical direction.
It is an object of the present invention to provide a generic hydroforming device which is capable of hydroforming a raw material with a conventional press machine.
It is another object of the present invention to provide a hydroforming device which has high speed and high responsiveness, resulting in high productivity.
It is a further object of the present invention to provide a hydroforming method in which a raw material is molded at high speed and high responsiveness, resulting in a highly productive method of hyrdroforming.
Briefly stated, the present invention provides a plurality of closing cylinder devices disposed between a bolster of a press machine and a bed containing a lower mold of a hydroforming device. An upper mold is attached to a slide of the press machine. The upper mold and lower mold come together to form a cavity having the shape of the exterior of the desired molded product. A closing block, being movable between a first position which is between the slide and a crown of the press machine, and a second position, which avoids the slide, permitting free movement of the slide from the crown to the lower mold. When a material to be hydroformed is place in the lower mold, the upper mold is lowered. The closing block is fit into its first position, thereby restricting movement of the slide in the vertical direction. A inner work pressure is provided by a fluid inside the material to be molded. The closing cylinder devices provide a pressure, based upon the inner work pressure, to maintain the cavity at the desired shape, preventing the upper mold and the lower mold from being separated by the inner work pressure.
According to an embodiment of the present invention, the present invention provides a hydroforming method using a press machine, comprising: providing a closing block movable between a first position and a second position; the first position being between a crown of the press machine and a slide of the press machine, preventing movement of the slide above a predetermined maximum; the second position avoiding the slide, thereby allowing the slide to freely move to a lower surface of the crown of the press machine; providing a lower mold attached to a bolster of the press machine; providing an upper mold attached to the slide; the upper mold and the lower mold coming together to form a cavity having a shape of a molded product; providing a plurality of closing cylinder devices between a bed and the bolster; providing a material to be molded into the lower mold; lowering the slide so that the upper mold and the lower mold form the cavity; moving the closing block into the first position, thereby preventing raising of the slide; activating the closing cylinder devices to provide a closing force, maintaining the cavity during operation of the hydroforming method; and providing a work inner pressure from a liquid supplied to an interior of the material to be molded, whereby the work inner pressure shapes the material to the shape of the cavity while the closing cylinder devices maintain the cavity.
According to another embodiment of the present invention, the present invention provides a hydroforming device using a press machine, comprising: a closing block movable between a first position and a second position; the first position being between a crown of the press machine and a slide of the press machine, preventing movement of the slide above a predetermined maximum; the second position avoiding the slide, thereby allowing the slide to freely move to a lower surface of the crown of the press machine; a lower mold attached to a bolster of the press machine; an upper mold attached to the slide; the upper mold and the lower mold coming together to form a cavity having a shape of a molded product; a plurality of closing cylinder devices between a bed of the press machine and the bolster; means for providing a work inner pressure in a material to be molded by the hydroforming device; a closing force, generated by the plurality of closing cylinder devices, being controlled to rise with a rise in the work inner pressure, thereby maintaining the cavity at a desired shape during hydroforming operations.
According to a feature of the present invention, a hydroforming method includes providing a closing block, which is freely movable in a horizontal direction, on the crown of a press machine. The closing block moves between a position between the crown and a slide and a position which avoids the slide. A plurality of closing cylinder devices, raising and lowering the bolster, are disposed between the bed and the bolster of the press machine. A cavity is formed from the upper mold, which is anchored to the slide, and the lower mold, which is anchored to the bolster. An axial piston freely advances towards and retreats from an end surface of a work which is stored within the cavity. A closing force, controlled to rise with a rise in a work inner pressure, is generated by the closing cylinders. The work inner pressure being caused from a liquid supplied to the interior of the work by the shaft pushing piston. With such a method, the time needed for closing is shortened and a rational molding is anticipated.
According to a further feature of the present invention, the plurality of closing cylinders are suitably selected and operated, thereby optimizing the closing time and responsiveness.
According to a further embodiment of the present invention, a generic press machine, equipped with a clutch brake and a crank shaft, has a hydroforming device between its slide and its bolster. The hydroforming device includes a mold having a separated top and bottom, opposing shaft pushing cylinders, and a closing cylinder.
According to a feature of the present invention, a hydroforming device, for processing a tube material by hydraulic pressure, includes a base plate anchored to a bolster of a press machine. A closing cylinder is anchored to an upper surface of the base plate. A guide part is erected on the upper surface of the base plate. A middle plate, having a sliding part which joins with the guide part, allows for up and down movement. A lower mold is anchored to an upper surface of he middle plate. A die plate is anchored to a slide of the press machine. An upper mold is anchored to a lower surface of the die plate. An axial cylinder is equipped with a key which joins with a key groove provided on a lower surface of the die plate.
According to the previous embodiment and feature of the present invention, a hydroforming device is mounted on a generic press machine equipped with a clutch brake and a crank shaft. The upper mold is anchored to the slide via the die plate. The closing cylinder is anchored to the upper surface of the bolster via the base plate. When raising the upper mold in order to supply material to the mold or to conduct maintenance, the slide of the machine press is raised. When conducting hydroforming, the slide is held at the bottom dead center, and the upper mold and the lower mold are closed by the closing cylinder. In other words, by the hydroforming device of the present invention, a generic press machine, equipped with a clutch brake and a crank shaft, is used as the press machine for conducting hydroforming. Therefore, because existing press machines can be used, there is no need to manufacture an exclusive device for conducting hydroforming. Advanced hydroforming can be introduced into a manufacturing facility at a relatively low cost.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.